The present invention relates to an apparatus for feeding documents into a scanning position on a platen of an electrostatic copying machine for scanning and discharging the documents after scanning.
Conventional electrostatic copying machines comprise a glass platen on which an original document is placed face down for scanning. A light image of the document is radiated onto an electrostatically charged photoconductive drum to form an electrostatic image. A toner is applied to the drum to form a toner image through electrostatic attraction. The toner image is transferred and fixed to a sheet of copy paper to provide a permanent reproduction of the original document. A presser plate or cover is provided which is raised to place the document on the platen and lowered onto the document to press the same against the platen for scanning.
Although this conventional arrangement is effective for copying bulky documents such as pages of bound books, it is inconvenient and slow for copying a number of sheet documents, especially where the documents are the same size. This is because it takes a considerable amount of time to raise the presser plate, remove a previous document, it any, place a new document on the platen and lower the presser plate onto the new document.
To speed up copying operations of a number of sheet documents, various automatic document feed systems have been developed and placed into practical application. There are generally two types of automatic feed systems. In the first type the documents are placed in a stack on a tray and automatically fed therefrom one by one onto the platen and discharged after scanning. In the second system the documents are manually fed one by one into a feed unit which feeds them to the platen for scanning and subsequent discharge.
The first system is advantageous where the documents are all of the same size and of medium thickness. However, where different sized documents or thick or thin documents are fed through such a device, various malfunctions such as failure to feed, feeding of more than one document at one time, jamming and tearing are common. Large documents which are expensive often jam, crease or tear while being fed through such a device.
While these drawbacks are overcome in the second type of system, the latter is inferior where it is desired to copy a large number of documents of the same size and medium thickness since the operation of manually inserting the documents into the feed unit one by one is quite slow compared to completely automatic feed.